ABSTRACT.Purpose: To study aqueous flare longitudinally in patients with Fuchs' heterochromic uveitis (FHU) and for comparison in another group with iris atrophy (non FHU). Methods: A new laser flare meter was used. Iris angiography was performed in most FHU patients. Results:The flare values in the affected eyes in the FHU group were always higher compared to the normal eyes and rather constant over time. Cataract surgery did not permanently change the flare values. Systemic -but not localsteroid therapy caused normalization of the flare. Iris angiography displayed leakage in all FHU eyes. Leakage from original vessels dominated although some newly-formed leaking vessels were observed. Conclusions:The results support the notion that FHU is a low grade, chronic, stable disease. Leaking iris vessels, original or newly-formed, are probably the source of the increased flare. Our hypothesis is that inflammation plays a major part. Atrophy per se does not enhance flare.